The fifth series of the program, which is aired by Channel 4, was promoted as "Big Brother gets evil".

Producers openly declared they were looking for confrontation and for Britain's first live sex in the series when they loaded the closed Big Brother house with sexual extroverts and muscle-bound aggressors.

Earlier in the week, viewers were treated to the sight of aspiring glamour model Michelle squirting herself a bikini using icing from a tube, and another housemate - lesbian and animal rights activist Kitten - was expelled for daubing political slogans on the interior walls of the house.

But the brawl, which took place early on Thursday, has now prompted a police investigation and calls for the show to be taken off the air, as well as a formal investigation from OfCom, Britain's broadcasting regulator.

Producers cut the broadcast at 3am as the confrontation worsened, and security guards were eventually sent in to drag participants apart.

South African archery champion Vanessa lunged at fellow contestant Nadia (who is transsexual, although this is not known to the other housemates) as the brawl worsened.

On Friday, Channel 4 announced it was cancelling the regular Friday night "eviction show" while further discussions took place. "The housemates are continuing to work through their differences and producers wish to give them sufficient time to come to a resolution as a group," a spokesman said.

Professor Steve Bennett, a media expert from Westminster University, said arguments could no longer be made that Big Brother was interesting or useful on a psychological or social level, and as such did not belong on a public broadcast network.

"What we're looking at here is anarchy without a reason; it's Colosseum-type material," he said.

"It's interesting if you have a reasonable cross-section of relatively normal people and you're watching how they cope in an enclosed space with people they don't know.

"But to set out to antagonise people is meaningless, valueless and empty. And probably cruel."